What does "SMART endurance training? mean?

[terry]

Dag Kaas is a Norwegian who has coached 12 different athletes who have won world championships in four different endurance sports. He has written: ”My experience as a coach tells me that to become world champion in endurance disciplines, you have to train SMART, and you have to train a LOT. One without the other is insufficient.”

We all know what it means to train a LOT.
1) What do we know about how to train SMART?
2) How do we tell when our pursuit of a LOT is not SMART?
3) How is SMART different for swimming than for other endurance disciplines?